In a known cutting plate carrier of this kind (German Pat. No. 25 06 902), the peripheral surface extends over an angle of about 135.degree. to 160.degree.. The remaining part of the cutting plate carrier extends parallel to the remaining side walls of the cutting plate. A cutting plate carrier of this kind is inserted in a recess of a holder of a machine tool. The simple external contour of the cutting plate carrier with an approximately semi-cylindrical peripheral surface and a plane base surface requires a recess of blind hole type in the holder, which can be produced very simply by means of an end-milling cutter. For this reason, users of lathe tools can make them themselves in case of need. They merely obtain the cutting plates with the associated cutting plate carriers, which can be manufactured in large numbers with great accuracy by means of suitable special machines, from another manufacturer. In this way, the users of the lathe tools can make the tool holders, such as turning tool holders, boring bars, boring heads and other special tools, themselves and need only then insert the prepared cutting plate carriers into the recesses which are simple to produce. The known cutting insert carriers in which the peripheral surface extends over an angle of 135.degree. to 160.degree. are always suitable, however, only for a certain mounting angle in the particular holder. This mounting angle is determined by the position which that cutting edge of the cutting plate which is operative at any given time is to adopt with respect to the axis of the holder or with respect to the workpiece. A certain cutting insert is always usable only for a certain mounting angle range. This has the disadvantage that not only must the manufacturer of the cutting plate carriers produce and keep in stock a plurality of differently shaped cutting plate carriers for a certain size of cutting plate, but the user must also order the cutting plate carriers according to the desired mounting angles and keep them in stock himself. Wrong orders and wrong stocks are moreover not out of the question.
Therefore, the problem underlying the invention is to provide a cutting plate carrier of the kind mentioned at the beginning insertable in a holder of a machine tool, in particular a lathe tool, and which, with a certain shape and size of cutting plate, is suitable for all the mounting angles that arise and moreover ensures optimum support of the cutting plate.
According to the invention, this is achieved in that the cutting plate carrier has a substantially circular plan, the axis of which coincides with the axis of the central screw thread, and the recess has a number of bearing surfaces for the lateral surfaces of the cutting plate which correspond to the number thereof, the bearing surfaces being arranged at an equal distance from the central screw thread.
The novel cutting plate carrier is supplied in the abovedescribed form to the user of a lathe tool, who then makes the desired lathe tool, for example a turning tool, a boring bar, a boring head or some other special tool, for himself using the cutting plate carrier. For this purpose, the user must merely provide in the holder a recess in the form of a blind hole, which can easily be produced, as well as a hole for the retaining screw. He can then mount or fit the cutting plate carrier in the desired angular position of rotation, so that the cutting edge of the cutting plate extends at the desired angle to the longitudinal axis of the holder. Advantageously, this angular position of rotation is also secured by means of a locating pin which is inserted in a locating bore provided for this purpose in the cutting plate carrier and in a corresponding bore in the holder. The protruding parts of the cutting plate carrier are then removed by stripping, grinding, milling or filing, which can also be associated at the same time with the finishing of the holder. Finally, it is only further necessary to insert the cutting plate into the carrier and fix it by means of the clamping screw. One and the same cutting plate carrier can be employed for the most diverse desired mounting angles of the operative cutting edge. This has the advantage that the manufacturer of the cutting plate carrier only has to make and keep in stock one type of carrier for a certain shape and size of cutting plate. The user can also now order larger numbers at the same time and keep them in stock himself, since he can use these for the most diverse mounting angles. Wrong orders and erroneous planning are avoided. At the same time, however, it is always ensured that the cutting plate carrier embraces the cutting plate on the greatest possible number of lateral surfaces and, consequently, ensures optimum support for the cutting plate. Furthermore, the cutting plate carrier, like the already known cutting plate carrier, has the advantage that it has no shoulders or recesses projecting beyond the cutting plate, so that swarf cannot settle, and that in the event of damage, which may occur when a cutting edge breaks, it can moreover be easily exchanged for a fresh one.
Advantageous developments of the invention are characterised in the sub-claims.